The present day habitability of Mars is an area of research that has exploded hugely in the last decade, to the extent that it s often hard to keep track of everything that s going on. This is by way of background material for my other articles on habitability of Mars.
Cyanobacteria have evolved complicated mechanisms to transform light energy into chemical energy during three billion years of existence. Cyanobacteria produce reducing power (NADPH) and chemical energy (ATP) for carbon dioxide fixation using only the most basic of ingredients: light and water.